JPH0418934A - Carbonaceous material for reduction of nitrogen oxide - Google Patents

Abstract

PURPOSE:To obtain a carbonaceous material for reduction of NOx having high activity and SO2 resistance by supporting a spinel type compd. contg. specified metals as a catalytic component on a carbonaceous material. CONSTITUTION:A spinel type compd. represented by a general formula AB2O4 (where A is Cu, Co or Ni and B is Al, Cr, Fe or Co) is supported on a carbonaceous material such as coal or coke. The resulting denitrating agent has high activity to the reduction and removal of NOx and the consumption of carbon by O2 coexisting with NOx is remarkably inhibited. Since the agent has improved SO2 resistance, denitration is stably and effectively carried out.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a carbon material for reducing nitrogen oxides, and in detail,
Nitrogen oxide reducing carbon is a denitration agent that consumes less carbon due to reaction with 0□, has excellent SO2 resistance, and can be advantageously used in the field of nitrogen oxide removal such as exhaust gas treatment. Regarding materials [Conventional technology] In recent years, a technology that uses denitrification agents that use carbon (carbonaceous materials) as a reducing agent to remove nitrogen oxides (NOX) from exhaust gas has been attracting attention. Development of a carbon material for reducing nitrogen oxides is underway.

In this NO removal technology that uses carbon as a reducing agent,
A method in which a gas to be treated such as exhaust gas is brought into contact with a carbonaceous material that does not support a catalyst component at a high temperature of 400"C or more, and a method in which a gas to be treated such as exhaust gas is brought into contact with a carbonaceous material that supports a catalyst component at a relatively low temperature of 400"C or less. Among these methods, the latter method is more practical because it is thermally advantageous, and there are differences in the type of supported catalyst components, differences in supported carbonaceous materials, and differences in preparation methods. Various carbon materials for reducing nitrogen oxides have been proposed depending on the situation.

In conventional carbon materials for reducing nitrogen oxides of this type, various carbon materials such as coal, charcoal, and activated carbon, as well as their processed products, are used as carbonaceous materials that serve as carriers and reducing agents. The catalyst component supported on the substance is
Conventionally, compounds such as nitrates, carbonates, acetates, and hydroxides of alkali metals such as K and transition metals such as Cu have been used (JP-A-54-1.61582, JP-A No. 58-58).
Publication No. 79522, Publication No. 5E179523, Publication No. 62
Publication No. 193633, Japanese Patent Publication No. 47-50981,
Publication No. 47-50982, etc.).

However, in these conventional carbon materials for nitrogen oxide reduction supporting alkali metal or transition metal compounds,
There were problems such as large consumption of carbon (carbonaceous material) by 02 coexisting in the gas to be treated such as exhaust gas; ■susceptibility to poisoning by SO□.

[Problem to be solved by the invention]

The present invention has been made in view of the above circumstances.

The purpose of the present invention is to solve the above problems and to
This is a carbon material for reducing nitrogen oxides containing a catalyst component with high reduction removal activity of OX>, and in addition, the consumption of carbon (carbonaceous substances) by 02 coexisting in the gas to be treated such as exhaust gas is significantly suppressed. Another object of the present invention is to provide a carbon material for reducing nitrogen oxides, which is a practically advantageous denitration agent having excellent performance such as significantly improved SO2 resistance.

[Means to solve the problem]

In order to achieve the above object, the present inventors have conducted intensive research and found that various carbonaceous materials (carbon or carbonaceous materials containing carbon as a main component) have a spinel-type compound consisting of a specific metal as a catalyst component. The inventors have discovered that a carbon material for reducing nitrogen oxides on which a specific component is supported is an excellent denitration agent that satisfies the above objectives, and based on this knowledge, the present invention has been completed.

That is, the present invention has the following general formula: This invention provides a carbon material for reducing nitrogen oxides, which is characterized in that a spinel type compound is supported on a carbonaceous material.

Hereinafter, the carbon material for reducing nitrogen oxides of the present invention will be described in detail while showing a suitable method for preparing it.

In the carbon material for reducing nitrogen oxides of the present invention, the raw material for preparing the carbonaceous material on which the spinel type compound is supported (hereinafter, this may be referred to as a carbonaceous raw material) includes:
As long as it is carbon that can be used as a NOx reducing agent or has carbon as its main component, various materials such as those commonly used in this field can be used. Specifically, for example, coals such as lignite and brown coal, and processed products of coals (
(e.g., coke, carbon black, char, activated carbon, etc.), petroleum-based carbon materials (e.g., petroleum coke, carbon black, char, activated carbon, resin carbide, etc.), plant-based carbon materials (e.g., charcoal and its processed products, various (activated carbon, etc.), animal-based carbon materials, etc. These may be used alone or in combination of two or more.

There is no particular restriction on the shape of the carbonaceous raw material used to support the spinel compound, but from the viewpoint of ease of handling, dispersibility of the spinel compound to be supported, etc., the average particle size is usually 1011 ITo. The following granular or powder forms are preferable.

In addition, by supporting the spinel type compound or its raw material components on powder or fine particles and then molding it into an appropriate shape, the uniform dispersibility of the spinel type compound serving as a catalyst can be significantly improved. can.

The nitrogen oxide reducing carbon material of the present invention has at least the above general formula [1], that is, AB20. It is important that the spinel type compound (complex oxide) represented by is supported.

As mentioned above, A in AB, 04 is Cu, C
o or Ni, but especially Cu and C.

is preferred. Note that two or more of these metal elements are AB20. may be mixed as A in .

AB, B in 04 is AI, C as described above.
r, Fe or Co. Note that two or more of these metal elements may be mixed as B in 8B204.

Specific examples of the spinel compound (ABz04) include C0Al2O4, C0Al2O4, N1Ah
O4, CuCrzOa, CoCrzOa, N1Cr
zOs, CuFezO4, CoFe, Oa, N1F
Examples include ezC14, CuCo, Oa, N1CozO4, and the like. Among these, especially CuAlz
On, CuC0zOn, CuFezO4, CoFez
Oa etc. are preferable.

Generally, ABZO type spinel compounds may have deformations such as a part of A or B being substituted with another element or becoming defective, but in the spinel compound of the present invention, Also, a part of A or B may be substituted with an element other than the above, or may be defective, within a range that does not impede the purpose of the present invention.

In addition, these spinel type compounds may be supported singly or in combination of two or more types.

In the carbon material for reducing nitrogen oxides of the present invention, the supporting rate of the spinel type compound cannot be uniformly defined because it depends on other conditions such as the type of the spinel type compound, but it is usually 0.5 to 0. It is appropriate to set the content to 50% by weight, preferably in the range of 1 to 20% by weight. If this loading rate is too low, sufficient catalytic performance cannot be ensured, while if it is too high, the ratio of carbonaceous material that serves as a NOx reducing agent will be low, resulting in a decrease in efficiency.

In addition, the carbonaceous substance in the carbon material for reducing nitrogen oxides of the present invention may contain other components other than the spinel compound, such as catalyst components and co-catalyst components, to the extent that it does not impede the purpose of the present invention. can also be carried.

There are no particular limitations on the method of supporting the spinel compound, and examples include (a) a method of supporting a predetermined spinel compound formed or prepared in advance on the carbonaceous raw material that becomes the carbonaceous material; (b) A raw material compound for a predetermined spinel type compound is supported on the carbonaceous material, and in any stage of the subsequent preparation process (usually the firing stage),
A method for forming a spinel compound on a carbonaceous material,
Alternatively, a combination of these methods can be adopted as appropriate.

When the above method (a) is employed, a powdered spinel compound is usually suitably used as the spinel compound for supporting. The size of this powder is desirably small from the viewpoint of improving dispersibility, and is usually 10 μm or less, preferably 1 μm or less. There are no particular restrictions on the method of supporting these spinel compounds, but
Usually, a kneading method in which the spinel type compound powder described above is kneaded with the carbonaceous raw material, preferably a powdered carbonaceous raw material, etc. can be suitably employed.

On the other hand, when adopting the supporting method mentioned above, the respective compounds that are the raw materials for the predetermined spinel type compound (ABzOs), that is, a mixture or composition of a compound of metal A (compound A) and a compound of metal B (compound B), are used. A mixed aqueous solution containing a compound (a composite compound of A and B may also be used), preferably each metal ion constituting a predetermined spinel type compound, is supported on the predetermined carbonaceous raw material by an impregnation method, a kneading method, etc. Alternatively, an aqueous solution containing appropriate ions consisting of compound A and compound B, preferably metal A, and an aqueous solution containing appropriate ions consisting of metal B are separately added to a predetermined carbonaceous raw material (sequentially). 2) After supporting the predetermined components using a method of supporting such as impregnation or kneading, or a method of supporting using a combination of the above,
In the subsequent firing step, various methods can be employed, such as a method of forming a spinel type compound on the carbonaceous material.

Examples of the compounds listed above and B used as raw materials for spinel-type compounds include salts such as nitrates, carbonates, acetates, and oxalates of the respective metals listed above.

Specifically, suitable examples of compounds include nitric acid w4 (II), nitrate w4 (II), nickel nitrate (II), nickel nitrate (
■), iron nitrate (■), copper acetate (■), cobalt acetate (I
I), nickel(II) acetate, etc.
Suitable examples of compound B include aluminum nitrate, cobal nitrate (III), chromium nitrate (■), iron nitrate (■), conolate acetate (■), and chromium acetate (II).
I), etc.

Among these, each nitrate is particularly preferred.

The ratio of each component supported is usually an atomic ratio of A/B of 1/2.
Although it is preferable to select the amounts so that they are close to each other, the present invention is not limited to this, and as long as a sufficient amount of the predetermined spinel type compound is formed, one or the other may be in excess.

After the predetermined components are supported as described above, the obtained supported material is molded into a desired shape, if necessary. The molding method is not particularly limited, and various methods such as known methods can be used.

Before molding, the carrier may be dried or its moisture content may be adjusted to make it suitable for molding.

When the carbonaceous raw material is a powder or fine particles, and the obtained support is in the form of powder or fine particles, an appropriate binder such as water, oil, or resin is usually added. For example, it is suitable to mold using a molding method such as an extrusion molding method, an agitation granulation method, or a transfer granulation method.

The amount of the binder to be used varies depending on the carbonaceous raw material, the type of binder, the molding method, etc., but it is generally appropriate to select it in the range of 0.5 to 50% by weight based on the carbonaceous component.

The size of the molded body is usually preferably about 0.5 to 15 mm, but is not limited to this.

That is, the shape and size of the carbon material for reducing nitrogen oxides of the present invention are not particularly limited, and the reaction apparatus using the same,
It may be determined as appropriate depending on the reaction operation, reaction method, etc. For example, when the carbon material for reducing nitrogen oxides of the present invention is used in a fluidized state such as in a moving bed, the particle size is usually about 0.5 mm to about 100 mm (preferably spherical). etc. can be suitably used. Such a spherical shape can be easily obtained by the above-mentioned granulation molding method.

Note that such a molding operation can be omitted for a supported material obtained by supporting the above-mentioned predetermined components on a carbonaceous raw material having an appropriate shape.

Further, if the carbonaceous raw material and the supported material are formed into an appropriate size, the carbonaceous raw material and the supported material may be subjected to appropriate pulverization or classification operations as necessary.

The supported material having an appropriate shape and size obtained as described above is dried if necessary and then subjected to a firing treatment to be finished as the carbon material for reducing nitrogen oxides of the present invention.

There are no particular restrictions on the method for this drying, and various methods can be used, but from the standpoint of simplifying the process, it is efficient to carry out this drying in a firing furnace prior to the next firing process. .

In this firing process, the predetermined support is placed in a firing device capable of realizing an inert atmosphere, such as a carbonization furnace, and after drying if necessary, it is usually placed in an inert gas atmosphere such as nitrogen, argon, helium, etc. It may be carried out under appropriate conditions as shown below, in an air stream or in a vacuum evacuation state, preferably in a nitrogen stream.

The reason why this firing treatment is performed in an inert atmosphere such as an inert gas is to avoid combustion of carbonaceous components, so if this is satisfied, it can be performed in various atmospheres. .

The firing conditions differ depending on whether the supported catalyst component has not yet become a spinel type compound or whether it is supported as a spinel type compound.

In the former case, the calcination is carried out under conditions such as a temperature at which the spinel type compound is effectively formed from the supported spinel type compound raw material components.

The temperature of firing while effectively forming a spinel type compound is usually about 700 to 1000°C, preferably 8°C.
00-900°C. If this temperature is too low, the catalyst raw material component will not be sufficiently converted into a spinel type compound, and in that case, the obtained carbon material for reducing nitrogen oxides will be
Even if it has OX reduction activity, the coexistence of 0□ does not sufficiently suppress the combustion of carbon X substances by 02, nor does it sufficiently improve SO□ resistance. .

On the other hand, a predetermined spinel type compound such as a supported material obtained by supporting the spinel type compound on the carbonaceous raw material (i.e., a supported material obtained by the supporting method of (a)) as a catalyst component is already supported. However, in this case as well, the mechanical strength such as hardness of the carbon material for reducing nitrogen oxides and the From the viewpoint of improving wear resistance, it is desirable to perform the firing in the same temperature range as above.

In any of the above-mentioned calcination treatments, if the calcination temperature is too high, the catalytic activity may decrease or the carbonaceous material reduction performance may decrease.

For both of the above firing treatments, the firing time varies depending on the temperature, the type of catalyst component, etc., but is usually about 1 to 10 hours, preferably about 2 to 5 hours.

These firing treatments may be performed in stages or continuously at various temperature modes, such as pre-firing at a relatively low temperature of about 200 to 500°C, prior to firing in the above temperature range. You can. By performing pre-calcination at a relatively low temperature, low boiling point components and thermal decomposition components in the support can be effectively removed at a relatively low temperature, resulting in improved catalytic performance in carbon materials for reducing nitrogen oxides. Effects such as being able to further improve the results may be obtained.

In the manner described above, the carbon material for reducing nitrogen oxides (denitration agent) of the present invention having a desired shape can be suitably produced.

The carbon material for reducing nitrogen oxides of the present invention utilizes at least the catalytic action of the spinel compound, and uses at least the carbon (carbonaceous material) as a reducing agent to reduce NOX (NO and NO□).
It is a highly active denitrification agent that effectively reduces and removes carbon (carbonaceous substances) due to the coexistence of 0□.
Consumption by combustion is significantly suppressed, and S-resistant
It is a practically extremely useful denitrification agent that has the advantage of significantly improved O2 properties, and therefore, it is especially
It can also be stably and effectively used for denitrification treatment of exhaust gas, etc. in which □ and SO2 coexist. Of course, the carbon material for reducing nitrogen oxides of the present invention is not limited to this, and can be suitably used as a denitrification agent for NOX-containing gases of various exhaust gases.

The reaction conditions when using the carbon material for reducing nitrogen oxides of the present invention as such a denitration agent vary depending on the catalyst components and the characteristics of the carbonaceous material (type of carbonaceous raw material). The reducing carbon material is usually suitably used under relatively mild conditions, for example, at a temperature of around 400°C or lower, similar to the conventional carbon material for reducing nitrogen oxides containing a catalyst component of this type. can do.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to these Examples, and various modifications and applications can be made without departing from the spirit of the present invention. is possible.

Example 1 145 g of copper nitrate and 349 g of aluminum nitrate were dissolved in IP water, and activated carbon (specific surface area: 1000 n) was added to the solution.
(/g) was immersed and dried to dryness, which was then calcined at 800'C for 2 hours in a nitrogen stream to obtain a carbon material for reducing nitrogen oxides (denitration agent) of the present invention.

At this time, X-ray diffraction revealed that the catalyst had a spinel structure (Cu
CozOa).

20 cc of the second product was placed in a fixed bed flow microreactor and its denitrification performance at 380°C was investigated. A chemiphotographic nitrogen oxide analyzer was used for the analysis of NO8, and a gas chromatograph was used for the analysis of CO1CO2. In addition, the gas composition in the denitrification reaction is NO = 300 ppm, 0□-3%
, SO□-oppm, nitrogen balance, and space velocity (S
V) was set to 1500 h-1.

The results are shown in Table 1.

Manufacturing evaluation was conducted in the same manner as in Example 1 using 145 g of comparative multilayer copper nitrate and 450 g of aluminum nitrate. However, the firing temperature was 500°C. At this time, no spinel structure was confirmed by X-ray diffraction, and the catalyst was a mixture of two types of simple oxides.

The results are shown in Table 1.

As shown in Table 1, under conditions without SO2, the catalyst has a long life even without the use of the present invention, but in the case of the denitrification agent (carbon material for reducing nitrogen oxides) of the present invention, the carbon consumption rate is significantly reduced. It can be seen that this has been improved.

Table 1 Example 2 Using the same denitrification agent as that used in Example 1, the gas composition was changed to NO = 300 ppm, Oz = 3%, SO□
The reaction was carried out in the same manner except that the nitrogen balance was -3ooppm and the denitrification performance was evaluated.

The results are shown in Table 2.

1 Denitrification rate = (1 - Outgoing NOx concentration / Incoming NOx concentration) x 100
(The smaller this value is, the better the performance is.) Example 3 A denitration agent was prepared in the same manner as in Example 1, except that 145 g of copper nitrate and 450 g of cobalt nitrate were used. We conducted an evaluation.

The results are shown in Table 2.

Example 4 A denitration agent containing CuFezOa was prepared in the same manner as in Example 1 except that 45 g of copper nitrate and 438 g of iron nitrate were used.
Evaluation was performed in the same manner as in Example 2 using this.

The results are shown in Table 2.

Table 2 Comparative Example 2 Evaluation was carried out in the same manner as in Example 2 using the conventional denitration agent that did not contain the spinel compound used in Comparative Example.

(Left below) As shown in Table 2, conventional denitrification agents deteriorate rapidly in the presence of SO□, whereas the denitrification agent of the present invention has a significantly improved lifespan. I understand.

That is, the spinel compound-containing denitrification agent of the present invention has SO
□It can be seen that the catalyst performance can be maintained for a long time even in the presence of odor≠.

〔Effect of the invention〕

According to the present invention, since a specific catalyst component called a spinel type compound made of a specific metal element is supported on carbon or a carbonaceous material mainly composed of carbon, nitrogen oxides (N
In addition to having high activity for the reduction and removal of OX ), even when 0□ coexists, carbon (carbonaceous material) due to 0
Consumption by combustion is significantly suppressed, and S-resistant
It has excellent performance such as significantly improved O2 properties, and has the advantage of being able to be stably and effectively used for denitration treatment of exhaust gas, etc. where 02 and SO□ coexist. It is possible to provide a carbon material for reducing nitrogen oxides which is a practically advantageous denitration agent.

Claims (1)

[Claims] 1. Expressed by the following general formula AB_2O_4 [I] (wherein A in the formula [I] represents Cu, Co or Ni, and B represents Al, Cr, Fe or Co). A carbon material for reducing nitrogen oxides, characterized in that a spinel type compound is supported on a carbonaceous material.